Mad question about electric clock

[Scott]

Genius. Could I 'customise' the message?

[Scott]

Very tempting. Plus a hard hat of course.

[Thomas Prufer]

Er ... you do know that some PCs and some laptops have hardware such that playing an (inaudible) sound file close to a radio clock will set it to an arbitrary time and date? At least there are sounds for DCF at 44 kHz, enter date&time on online site, d/l sound, play it. Also, arduinos etc can send at these low frequncies, enough to affect clocks at short range. Programs downloadable from the great interweb.

Just academic information:-)

Thomas Prufer

[DJC]

The cheap ones do. First time I noticed because I was working late and was puzzled by the wirring noise from somewhere in the room. Took a while to realise it was the clock. Nowadays I know it's time for bed when I hear the clock start its reset sequence at ~01:15. Also makes a mess of the change to summer-time: checks time at 01:15 correct, clocks go forward at 02:00, but it won't check the time again until the next day. It also has a tempreture displlay which is useless because someone didn't understand °C and °F. Display goes from -20 to +140 but that is °C so the needle never really moves more than a few (angular) degrees around the 20°C mark.

[T i m]

<snip>

It was perfectly clear ... not much chance of that now he's already showed himself up. ;-)

As others have suggested, it was *very* clear to anyone reading for fact and not just triggering of a couple of keywords. ;-)

FWIW, we have an 'analogue' 'radio controlled clock' (and not a clock radio <g>) and it typically works very well indeed. It either pauses for an hour or runs fast to catch up an hour and we have only ever seen it doing anything 'strange' a few times in 10+ years.

One strange mode is when the battery is nearly flat and it can't reliably crank the hands uphill and the other we saw for the first time recently where it went a bit crazy and wound itself forward about

10 mins and then settled down again. It had corrected itself again by the morning. I was playing with a WiFi access point that was pretty close to the clock so that might have had something to do with it?

I built one of the 7 segment LED display radio controlled clocks years ago that had a remote radio receiver and that also worked pretty well for a long time. It was interesting setting up the radio as you tuned it using an audio earpiece and you could clearly hear the 'chiff-chiff' on the second and the extra bits on the hour. ;-)

Cheers, T i m

[Harry Bloomfield]

Bob Eager explained :

There is a fast code at 59 seconds epoch and a slow code. The slow code offers one data bit sent every second, so can take up to 1 minute 59 seconds to get a complete data set. Any problem during that time, means the data collection begins again from the minute epoch. The check sum is provided in the seconds before the 59 second, with a long burst at the 00 epoch.

I think most clocks use the slow code, hence it can take a while to get a valid data set.

I once studied the subject and exchanged a few letters with the GPO (who then operated it), to devise a software system to decode it.

[Harry Bloomfield]

No extra bits on the hour, it went silent for the final seconds before. With a good ear, pencil and paper, you could decode the data by listening.

[Andrew Gabriel]

The fastcode in second 59 was switched off decades ago.

[Bob Eager]

Mine is from recollection, when I supervised a student who was implementing such a clock for a project.

[T i m]

Is there anything out there that states just what it does OOI?

I'm pretty sure I heard 'extra' stuff on the min and possibly the hour, not it just catching up from any 'gap'?

Mind you, it was a long time ago now.

I still have my Yupiteru MVT-700 scanner, could that still hear such signals?

Cheers, T i m

[Bob Eager]

A cursory look at the NPL website:

[T i m]

Yeah, I found that after replying to Harry. ;-)

Not sure I fully understand it though. ;-(

My scanner only goes down to 100KHz. ;-(

Cheers, T i m

[whisky-dave]

No it wasn't and you were to brain dead to realise.